Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and a storage medium.
Description of the Related Art
Conventionally, there is a technique (monochromatization into black) to detect a gray character from bitmap image data sent from a PC or the like, and to convert the detected gray character into a character represented only in black (K value) (e.g., Japanese Patent Application No. 2014-100846). Specifically, monochromatization into black is performed in such a procedure as below.
1) Attention is focused on each pixel of bitmap image data and a window (predetermined area) with the pixel of interest as a center is set.
2) In the case where the number of pixels whose color is the same as that of the pixel of interest is large, the number of pixels in a similar color is small, and the number of pixels in different colors is large in the set window, the pixel of interest is determined to be a pixel belonging to a “character”.
3) Then, in the case where the pixel of interest determined to belong to a “character” is gray (R=G=B), the pixel of interest is determined to be a pixel belonging to a “gray character” and the pixel is monochromatized into black.
Japanese Patent Application No. 2014-100846 is a document that is not disclosed, and therefore, to be strict, it is not possible to call the technique the prior art, but the technique described in Japanese Patent Application No. 2014-100846 is the technique closest to the technique of the present invention, and therefore, the technique is explained as the prior art.
In the case where each pixel constituting a gray character included in bitmap image data is analyzed by making use of the technique of Japanese Patent Application No. 2014-100846 described above, a pixel determined to “belong” to the gray character and a pixel determined to “not belong” to the gray character are included therein as a result. In other words, a pixel located on the end (edge) of the gray character is determined to belong to the gray character and a pixel located at the center (non-edge) of the gray character is determined to not belong to the gray character.
As described above, such a situation is brought about in which some pixels, which are located in the positions up to a certain position, of the pixels constituting the gray character are determined to belong to the gray character, but the next and subsequent pixels are determined to not belong to the gray character. As a result of this, a pixel on which processing to monochromatize into black is to be performed and a pixel on which the processing is not performed are adjacent to each other despite the fact that both pixels constitute the same gray character, and therefore, the boundary (difference in step) becomes conspicuous and the image quality will deteriorate.